In the New York City neighborhood known as "Hogan's Alley," pugilist Lefty O'Brien becomes engaged to local tomboy Patsy Ryan, against the wishes of her father, Michael. During a championship fight with Battling Savage, Lefty breaks his left hand and leaves his opponent close to death. Believing he is in trouble with the law, Lefty finds refuge with Patsy, but her father turns the young couple out. When Patsy is injured, Michael seeks help from wealthy Dr. Emmett Franklin, who takes more than a professional interest in his patient. He invites Michael and Patsy to a dinner that turns into a wild party. Lefty crashes the event and demands that Patsy leave with him; she refuses and returns his engagement ring. The doctor invites father and daughter to his mountain lodge, then leaves Michael stranded at the railroad station. Lefty comes to Michael's aid and they pursue the train in an automobile. The two vehicles collide and a portion of the train breaks loose. Patsy is trapped inside a runaway car, and Lefty employs an airplane to rescues her. The two lovers marry and make their fortune in plumbing, much to Michael's pleasure.—AFI